1. Field of the Invention
This invention relates generally to electrochemical deposition, and more particularly to selective electrochemical deposition on specific portions of a surface using microdroplets of solution rather than a standing pool of solution or immersion in a bath of solution.
2. Related Art
The development of miniaturized circuitry has made it necessary to selectively deposit various materials over certain areas of, for example, printed circuits. One method for accomplishing this is electrochemical deposition. However, existing methods of electrochemical deposition do not allow selective deposition over limited portions of a printed circuit. Under conventional methods, for example, a substrate to receive deposition is masked using photolithography. This masking serves to cover areas not being deposited. The masked substrate is then submerged, or otherwise dipped or immersed, in an electrochemical bath of electrolyte solution. The substrate is biased negatively, for example, such that electrochemical deposition occurs over the entire surface of the substrate. The masking is then removed.
This method results in a significant amount of unwanted deposition over the previously masked areas, in which material to be deposited is lost as waste. Additional loss of electrolyte solution occurs when the wet substrate is removed from the electrochemical bath and drained and dried.
The inventors have found no similar method of electro-deposition employed in research, in industrial use, nor in the patent prior art compared to the present invention. It is an object of the present invention to achieve a method of electrochemical deposition that deposits material on targeted areas only—i.e., a method that does not require masking, does not require submersion or immersion, and which requires minimal loss or waste of unwanted material following the deposition process. It is a further object of the present invention to achieve a method of electrochemical deposition that eliminates the need to submerge and then rinse or drain the substrate, reducing consumption and waste of the electrolytic solution, and eliminating the need for exposure of the entire surface of the substrate to the chemical bath.